Neupane Hari Krishna, Adhikari Narayan Prasad
Amrit Campus, Institute of Science and Technology Tribhuvan University, Kathmandu, Nepal.
Central Department of Physics, Institute of Science and Technology Tribhuvan University, Kathmandu, Nepal.
J Mol Model. 2021 Feb 12;27(3):82. doi: 10.1007/s00894-021-04690-8.
We have studied structure, electronic, and magnetic properties of water adsorbed vdW heterostructure graphene/MoS (w-(HS)G/MoS) and its C sites vacancy defects materials (w-C-(HS)G/MoS) by using a spin polarized density functional theory (DFT) method of calculations within DFT-D2 approach to take in to account of vdW interactions. All the structures are optimized and relaxed by BFGS method using computational tool Quantum ESPRESSO package. By structural analysis, we found that both w-(HS)G/MoS and w-C-(HS)G/MoS are stable materials. The stability and compactness of these materials decrease with an increase in their defects concentrations. From band structure calculations, our findings show that w-(HS)G/MoS has a metallic nature, and there is formation of n-type Schottky contact of barrier height 0.42 eV. Also, the left 1C atom vacancy defects in w-(HS)G/MoS (L1C-w-(HS)G/MoS) and center 1C atom vacancy defects in w-(HS)G/MoS (C1C-w-(HS)G/MoS) materials have no band gap for up and down spin electronic states, indicating that they have also a metallic nature. On the other hand, 2C atom vacancy defects in w-(HS)G/MoS (2C-w-(HS)G/MoS) has a small band gap for up spins states and no band gap for down spin electronic states which means that the band structure resembles with half metallic nature. Thus, the endowment of metallic nature decreased with increase in the concentrations of defects in structures. To study the magnetic properties in materials, DOS and PDOS calculations are used, and we found that non-magnetic w-(HS)G/MoS material changes to magnetic in all the three different L1C-w-(HS)G/MoS, C1C-w-(HS)G/MoS, and 2C-w-(HS)G/MoS materials with vacancy. L1C-w-(HS)G/MoS, C1C-w-(HS)G/MoS, and 2C-w-(HS)G/MoS have magnetic moments of + 0.21 μ/cell, + 0.26 μ/cell, and - 2.00 μ/cell, respectively. The spins of electrons in 2s and 2p orbitals of C atoms give a principal effect of magnetism in w-C-(HS)G/MoS materials.
我们采用自旋极化密度泛函理论（DFT）方法，并结合DFT-D2方法来考虑范德华相互作用，研究了水吸附的范德华异质结构石墨烯/MoS（w-(HS)G/MoS）及其C位空位缺陷材料（w-C-(HS)G/MoS）的结构、电子和磁性性质。所有结构均使用计算工具Quantum ESPRESSO软件包中的BFGS方法进行优化和弛豫。通过结构分析，我们发现w-(HS)G/MoS和w-C-(HS)G/MoS都是稳定的材料。这些材料的稳定性和致密性随着缺陷浓度的增加而降低。从能带结构计算结果来看，我们的研究结果表明w-(HS)G/MoS具有金属性质，并且形成了势垒高度为0.42 eV的n型肖特基接触。此外，w-(HS)G/MoS中的左1C原子空位缺陷（L1C-w-(HS)G/MoS）和w-(HS)G/MoS中的中心1C原子空位缺陷（C1C-w-(HS)G/MoS）材料对于自旋向上和向下的电子态都没有带隙，这表明它们也具有金属性质。另一方面，w-(HS)G/MoS中的2C原子空位缺陷（2C-w-(HS)G/MoS）对于自旋向上的态有一个小带隙，而对于自旋向下的电子态没有带隙，这意味着能带结构类似于半金属性质。因此，随着结构中缺陷浓度的增加，金属性质的赋予程度降低。为了研究材料中的磁性性质，我们进行了态密度（DOS）和投影态密度（PDOS）计算，并且我们发现非磁性的w-(HS)G/MoS材料在所有三种不同的有空位的L1C-w-(HS)G/MoS、C1C-w-(HS)G/MoS和2C-w-(HS)G/MoS材料中都变成了磁性材料。L1C-w-(HS)G/MoS、C1C-w-(HS)G/MoS和2C-w-(HS)G/MoS的磁矩分别为+0.21 μ/晶胞、+0.26 μ/晶胞和 -2.00 μ/晶胞。C原子2s和2p轨道中的电子自旋在w-C-(HS)G/MoS材料中产生了主要的磁效应。
